A bearing is customarily used to support a rotating shaft of a motor when a rotor rotates around the stator circumferentially.
There are two general types of bearings: a ball bearing and a self-lubricating bearing.
Please refer to FIGS. 1(a) and 1(b). The ball bearing 1 includes an inner ring 13 which includes a groove as a raceway, an outer ring 12 which also includes a groove as a raceway and a plurality of balls 11 which are inserted between respective grooves of the inner and outer rings. The inner ring 13 is usually fixed to a rotary shaft 21 of a rotor, and the outer ring 12 is fixed to a base or a stator 23. The upper side of the ball bearing 1 is urged against a spring 22 for facilitating smooth rotation.
Upon rotating the shaft 21, the balls 11 of the ball bearing 1 race around the grooves inward the outer ring 12 and outward the inner ring 13. After the ball bearing 1 is used for a certain period of time, the fatigue of the metal material is customarily found, thereby causing the balls 11 and the surface of the inner ring 13 or the outer ring 12 to be abraded.
Referring to FIGS. 2(a) and 2(b), a self-lubricating bearing 3 manufactured of polymeric material is usually in a shape of a sleeve and it contains minute passages or channels carrying therein the lubricating oil 31 such that the oil 31 can be deposited on the shaft 21 by diffusion into the inner wall 32 upon rotation of the shaft 21. The inner wall 32 of the self-lubricating bearing 3 usually contacts with a rotary shaft 21, and the outer wall 33 is fixed to a base 23.
In contrast, the ball bearing 1 can perform under heavy loads and has a long life; however, it is costly and has the disadvantage of being abraded. The self-lubricating bearing 3 has good self-lubricating properties to reduce abrasion and is cheaper than the ball bearing; however, it generally incapable of being operated with large loads and its life is not very long.
It is therefore tried by the present invention to overcome the above-described problems.